13. TEXTURED YARNS.

The section of "Yarn Production and Properties," presents information about the production methods of textured yarn including that of false-twist machines. There are two machines, that work on the friction-twisting principle. Several new patents include methods of friction-twisting, but perhaps, it is important that although all the patentees produce false-twist machines, none of them makes a friction twister. One of the researchers has given a mathematical analysis of the development of false twist at the start-up of the process, which is probably the most complete treatment available till now.